Printing postscript from the [BLT] graph widget is pretty easy, much like you can print from canvas widgets.  The postscript options are described pretty well in the HTML documentation.

  .g postscript configure -landscape yes -maxpect yes
  .g postscript output myFile.ps

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There are different, less well documented approaches to printing under Windows at 
[BLT - graph - printing from Windows]

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[Category BLT]